The present invention relates to a vehicular headlamp having an inclination measuring unit for determining whether or not the direction of irradiation of the headlamp, that is, the angle of irradiation of the headlamp in a horizontal plane, is correct. More particularly, the invention relates to a vehicular headlamp having an inclination measuring unit with which the angle of irradiation of the lamp can be corrected with ease when it is found not to be correct.
By way of example, a movable reflector type headlamp will be described in which a reflector is tiltably supported in the lamp body. As shown in FIG. 11, the rear wall of the reflector 202 is supported at three points on the lamp body 201, namely, with two aiming screws 203 and 204 extending in the axial direction of the headlamp, and with a swinging fulcrum 205. (Since FIG. 11 is a front view of the reflector, the aiming screws 203 and 204 extend perpendicular to the surface of the drawing.) More specifically, the aiming screws 203 and 204 are threadably and rotatably supported on the rear wall of the lamp body 201. The reflector supporting points of the aiming screws 203 and 204 are arranged so that two straight lines connecting the supporting points and the swinging fulcrum 205 form right angles, for instance. The aiming screws 203 and 204 are turned to swing the reflector 202 about the horizontal axis L.sub.X and the vertical axis L.sub.Y, respectively, thereby to adjust the angle of irradiation of the headlamp. In FIG. 11, reference numeral 206 designates a light source, namely, a light bulb fitted in the reflector 202.
On the other hand, a so-called movable unit type headlamp (not shown) is available in which a lamp-body reflector unit is tiltably supported on the lamp housing. In this case, the reflector is integrally formed on the inner wall of the lamp body. In the movable unit type headlamp, similarly as in the movable reflector type headlamp, the lamp-body reflector unit is supported on the lamp housing with one swinging fulcrum and two aiming screws. The aiming screws are turned to tilt the lamp-body reflector, thereby to adjust the angle of irradiation of the headlamp.
That is, by turning the two aiming screws, a tilting member (the reflector in the case of the movable reflector type headlamp and the lamp-body reflector in the case of the movable unit type headlamp) on which the light reflecting surface is formed is tiltably adjusted to set the direction of irradiation of the headlamp. The tilting member thus can be swung vertically (about the horizontal axis) and horizontally (about the vertical axis) with respect to a reference member (the lamp body in the case of the movable reflector type headlamp and the lamp housing in the case of the movable unit type headlamp) to adjust the angle of irradiation of the headlamp.
Recently, a variety of devices for measuring the angle of irradiation of a headlamp in a horizontal plane have been proposed. In this regard, the present applicant has disclosed various such measuring devices in Japanese Patent Application No. 154630/1988 and Japanese Utility Models Applications Nos. 98397/1988, 121576/1988 and 43979/1989.
However, the conventional measuring devices have certain drawbacks. First, the measuring devices are generally designed so that a measuring unit for measuring the amount of inclination of the tilting member in a horizontal plane is provided between the tilting member and the reference member. The measuring unit is positioned on the upper portion of the headlamp so as to facilitate the reading of the indication. Accordingly, the resultant headlamp is relatively large in height. This goes against the recent tendency to reduce the height of a headlamp as much as possible. In a movable reflector type headlamp, the measuring unit is arranged in the lamp body, and is thus inconvenient to read.
The aforementioned Japanese Patent Application No. 154630/1988 has proposed a measuring unit having a scale section protruding behind the reference member. However, the measuring unit is still disadvantageous in that it is necessary to form holes in the reference member to mount the measuring unit, which is rather troublesome to accomplish. In addition, adjustment is rather difficult when the measuring unit is installed on the headlamp.
Moreover, when the measuring device is disposed between the tilting member and reference member, it is generally necessary to provide a fine adjustment mechanism to adjust the scale of the measuring device for zero-point adjustment. This significantly complicates the structure of the device and complicates its use.